Method of fabricating lead frame and method of fabricating semiconductor device using the same, and lead frame and semiconductor device using the same

ABSTRACT

A method of fabricating a lead frame for a semiconductor device having a semiconductor chip resin-sealed therein. The lead frame includes a lead to be electrically connected to the semiconductor chip within sealing resin and to be sealed into the sealing resin such that at least a part of its mounting surface is exposed from the sealing resin. The method includes a lead forming step for forming the lead, and a side edge coining step for subjecting a side edge of a sealed surface, which is a surface on the opposite side of the mounting surface, of the lead to coining processing from the side of the sealed surface, to form a slipping preventing portion. The slipping preventing portion is to project sideward from the lead and to have a slipping preventing surface between the mounting surface and the sealed surface of the lead.

This is a Divisional of U.S. application Ser. No.: 10/988,551, filedNov. 16, 2004 now U.S. Pat. No. 7,224,049, the subject matter of whichis incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of fabricating a lead framefor a semiconductor device fabricated by resin-sealing a semiconductorchip and a method of fabricating a semiconductor device using the same,and such a lead frame and a semiconductor device using the same.

2. Description of Related Art

In order to high-density mount a semiconductor device on a wiringsubstrate, a package for high-density mounting allowing surface-mountingon the wiring substrate by eliminating extension of a lead from amolding resin package and exposing a lead (a terminal portionelectrically connected to a semiconductor chip) of a lead frame to alower surface of the package has been conventionally used. Known as sucha package for high-density mounting have been leadless packages such asQFN (Quad Flat Non-leaded Package) or SON (Small Outlined Non-leadedPackage).

In the packages in these forms, a lower surface of the lead sealed withmolding resin, together with the semiconductor chip, is exposed to thelower surface of the package, so that the lead easily slips off themolding resin. Therefore, the lead can be prevented from slipping off byforming the lead into a reverse tapered shape and forming a step on aside surface of the lead.

In order to form the lead having such a cross-sectional shape, the leadframe has been conventionally processed by etching. However, a long timeis required for the processing. Therefore, the fabrication of the leadframe using a precision press metal mold has been recently proposed, asdisclosed in U.S. Pat. No. 6,664,133.

In the method disclosed in the U.S. Patent, the lead frame is fabricatedby subjecting a metal plate serving as a material for the lead frame topunching processing and pressing processing using a punch from the sideof a lower surface of the lead frame, and stepped shapes for slippingprevention are respectively formed at a front end and on a side surfaceof the lead.

More specifically, in the method disclosed in the US patent, the centerof the lead is made wide, and a side edge of the center is subjected topressing processing using a punch from the side of a lower surface ofthe lead, thereby forming a two-step shape for slipping prevention. Forthe purpose of preventing a burr from occurring in the case of pressingprocessing from the side of the lower surface, a constricted part isformed on a side surface between the center and the base of the lead.

In the method disclosed in the US patent, the shape of the lower surfaceof the lead obtained by the punching processing is lost in performingthe pressing processing from the side of the lower surface. Therefore,the lower surface of the lead for making electrical connection to theexterior may not have a desired shape (e.g., a linear shape).

In order to prevent the metal burr occurring in the case of frameprocessing, the constricted part must be formed between the center andthe base of the lead, so that the shape of the lead first formed by thepunching processing is complicated. Consequently, required as a metalmold (a punch) for the punching processing is one which is subjected tocomplicated processing.

In the prior art disclosed in the US patent, therefore, a lot of metalmolds having a precise and complicated structure are required, so thatthe fabrication costs of the metal molds pile up. As a result, thefabrication cost of the lead frame and therefore, the fabrication costof the semiconductor device rises.

On the other hand, in the above-mentioned semiconductor package, apackage (e.g., HQFN: Heat Sinked Quad Flat Non-leaded Package) having astructure for exposing an island (a chip support having a semiconductorchip carried thereon) of a lead frame on a lower surface of the packagehas been put to practical use in order to enhance heat dissipatingproperties.

In the package having such a structure, a lower surface of the island,together with the semiconductor chip, sealed with molding resin isexposed to the lower surface of the package, so that the island easilyslips off the molding resin. Therefore, an end surface of the island ismade to have a reverse tapered shape, or the island is formed with astep to prevent the island from slipping off.

The island having such a cross-sectional shape has been formed byetching, as disclosed in US Patent Application Publication No.2002/0096790A1, for example.

Since running cost is required to process the end surface of the islandby etching, however, the lead frame cannot be fabricated at low cost.

In the prior art disclosed in the US Patent Application Publication, inorder to expose both the lead and the island from the lower surface ofthe package, they have been arranged so as to be flush with each otherbefore resin sealing. When the lead is interposed between upper andlower metal molds to supply molding resin to a cavity between the metalmolds, a pressing force from the upper metal mold is not exerted on theisland, so that the resin detours toward the lower surface of theisland. Therefore, the lower surface of the island is insufficientlyexposed, thereby not obtaining a desired cooling effect.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of fabricatinga lead frame capable of forming a slipping preventing structure of alead at low cost, and a method of fabricating a semiconductor deviceusing the same.

Another object of the present invention is to provide a lead framecapable of forming a slipping preventing structure of a lead at lowcost, and a semiconductor device using the same.

Still another object of the present invention is to provide a method offabricating a lead frame having a slipping preventing structure of achip support at low cost, and a method of fabricating a semiconductordevice allowing cost reduction by using the same.

Yet still another object of the present invention is to provide a leadframe which can be fabricated at low cost while having a slippingpreventing structure of a chip support, and a semiconductor deviceallowing fabricating cost reduction by using the same.

A further object of the present invention is to provide a method offabricating a lead frame capable of reliably exposing a lower surface ofa chip support from sealing resin, and a method of fabricating asemiconductor device using the same.

A still further object of the present invention is to provide a leadframe capable of reliably exposing a lower surface of a chip supportfrom sealing resin, and a semiconductor device using the same.

A method of fabricating a lead frame according to a first aspect of thepresent invention is a method of fabricating a lead frame for asemiconductor device having a semiconductor chip resin-sealed therein,the lead frame including a lead to be electrically connected to thesemiconductor chip within sealing resin and to be sealed into thesealing resin such that at least a part of its mounting surface isexposed from the sealing resin. The method including a lead forming stepfor forming the lead, and a side edge coining step for subjecting a sideedge of a sealed surface, which is a surface on the opposite side of themounting surface, of the lead to coining processing from the side of thesealed surface, to form a slipping preventing portion projectingsideward from the lead and having a slipping preventing surface betweenthe mounting surface and the sealed surface of the lead.

According to this method, the slipping preventing portion which sticksout sideward from the lead is formed by the coining processing from theside of the sealed surface of the lead. The slipping preventing portionhas the slipping preventing surface at an intermediate position of theplate thickness of the lead (between the mounting surface and the sealedsurface). Accordingly, the sealing resin detours toward the mountingsurface of the slipping preventing surface at the time of resin sealing.Consequently, the lead can be prevented from slipping off the sealingresin.

Since the slipping preventing portion is formed by the coiningprocessing from the side of the sealed surface of the lead. Accordingly,a sag on the side of the mounting surface of the lead can be reprocessedto be flat at the time of the coining processing. Consequently, it ispossible to reduce the detour of the sealing resin toward the mountingsurface of the lead. Further, the shape of a metal mold for the coiningprocessing may be simpler than a metal mold for pressing processing of alower surface in the prior art disclosed in U.S. Pat. No. 6,664,133.Therefore, it is possible to reduce the fabrication costs of the leadframe and the semiconductor device using the same.

Since the sealed surface of the lead is sealed into the resin, the sideedge thereof need not finally have a liner shape. Accordingly, an areacorresponding to an outer lead of the mounting surface of the lead (aportion exposed to the lower surface of the sealing resin to makeexternal connection) is subjected to the coining processing, therebymaking it possible to form the slipping preventing portion.Consequently, the lead need not be previously provided with a wide partin order to form the slipping preventing portion. Accordingly, the leadfirst formed by the punching processing or the like can be made to havea simple shape (a linear shape) having no substantial steps (steps asviewed from the top) on its side surface. From this point, therefore, itis also possible to reduce the fabrication cost as well as to form theslipping preventing portion without causing a burr.

It is preferable that the lead forming step includes a step of formingthe lead in a longitudinal shape. In this case, it is preferable thatthe side edge coining step includes a step of forming the slippingpreventing portions at a plurality of positions spaced apart from oneanother in the longitudinal direction of the lead. In this method, thelead is formed in the longitudinal shape, and the slipping preventingportions are formed at the plurality of positions spaced apart from oneanother in the longitudinal direction of the lead. This makes itpossible to effectively prevent the lead from slipping off the sealingresin along the longitudinal direction.

When the lead forming step includes a step of forming the lead in alongitudinal shape, the side edge coining step may include a step offorming the slipping preventing portions at both side edges of thesealed surface of the lead. According to this method, the slippingpreventing portions are formed at both the side edges of the lead in thelongitudinal shape. Consequently, the lead can be more effectivelyprevented from slipping off.

It is preferable that the lead forming step includes a punchingprocessing step for a metal plate which is a material for the leadframe. According to this method, the lead and the slipping preventingportions can be formed by a series of press workings. It is preferablethat the punching processing is performed from the side of the mountingsurface of the lead. Consequently, no burr occurs on the mountingsurface of the lead.

A method of fabricating a semiconductor device according to a firstaspect of the present invention includes: a step of fabricating the leadframe by the above-mentioned method; a step of electrically connectingthe sealed surface of the lead and the semiconductor chip to each other;a step of resin-sealing the lead frame, together with the semiconductorchip, such that at least a part of the mounting surface of the lead isexposed; and a step of cutting away an unnecessary part of the leadframe. It is preferable that the resin sealing step includes a step ofsealing the semiconductor chip and the lead frame with the sealing resinsuch that an end surface of the sealing resin crosses the slippingpreventing portion.

A lead frame according to a first aspect of the present invention is alead frame for a semiconductor device having a semiconductor chipresin-sealed therein. The lead frame includes a lead to be electricallyconnected to the semiconductor chip within sealing resin and to besealed into the sealing resin such that at least a part of its mountingsurface is exposed from the sealing resin, and a slipping preventingportion formed by coining processing from the side of a sealed surface,which is a surface on the opposite side of the mounting surface, of thelead and projecting sideward from the lead. The lead frame is high inreliability and can be fabricated at low cost because the resin does notdetour toward the mounting surface of the lead.

The lead may be formed in a longitudinal shape. In this case, it ispreferable that the slipping preventing portions are formed at aplurality of positions spaced apart from one another in the longitudinaldirection of the lead.

Furthermore, it is preferable that when the lead is formed in alongitudinal shape, the slipping preventing portions are formed at bothside edges of the sealed surface of the lead.

A semiconductor device according to a first aspect of the presentinvention includes: the above-mentioned lead frame; the semiconductorchip electrically connected to the lead frame; and the sealing resin forsealing the semiconductor chip and the lead frame such that the mountingsurface of the lead is exposed. The semiconductor device may furtherinclude a bump for electrically connecting the lead frame and thesemiconductor chip to each other wirelessly. It is preferable that thesealing resin has its end surface formed so as to cross the slippingpreventing portion.

A method of fabricating a lead frame according to a second aspect of thepresent invention is a method of fabricating a lead frame for asemiconductor device having a semiconductor chip resin-sealed therein,the lead frame including a chip support to have the semiconductor chipcarried thereon and having one surface serving as an exposed surfaceexposed from the sealing resin and the other surface serving as a sealedsurface sealed into the sealing resin. The method includes a step ofshaping a metal plate to form the chip support, and a step of subjectingan edge of the chip support to coining processing from the side of theexposed surface or the sealed surface, and forming a slipping preventingportion sticking out sideward from the edge of the chip support at aposition between the exposed surface and the sealed surface of the chipsupport.

According to this method, the slipping preventing portion is formed bysubjecting the edge of the chip support to the coining processing fromthe side of the exposed surface or the sealed surface. Accordingly, theslipping preventing portion can be formed in steps at lower cost, ascompared with that in a case where the slipping preventing portion isformed in an etching step. This allows the fabrication cost of the leadframe to be reduced.

The slipping preventing portion formed by the coining processing sticksout sideward from the edge of the chip support at an intermediateposition of the plate thickness of the chip support (a position betweenthe exposed surface and the sealed surface). Accordingly, the sealingresin detours toward the exposed surface at the time of resin sealing.This makes it possible to prevent the chip support from slipping off thesealing resin.

The coining processing for the edge of the chip support may be performedfor the whole area at the edge or may be performed for a part of theedge.

It is preferable that the step of forming the chip support includes apunching step for punching a hole in the metal plate in the shape of thechip support from the exposed surface to the sealed surface of the chipsupport. According to this method, the chip support is formed bypunching a hole in the metal plate which is a material for the leadframe from the side of the exposed surface. Consequently, the chipsupport and the slipping preventing portion can be formed using a pressworking apparatus. Therefore, the lead frame can be fabricated at lowcost.

Furthermore, the chip support is formed by the punching processing fromthe side of the exposed surface, so that no burr projecting from thesealing resin occurs, thereby making it possible to bring the exposedsurface into a flat surface and prevent the resin from adhering to theexposed surface of the chip support.

In order to more effectively prevent the resin from detouring toward theexposed surface of the chip support, it is preferable that almost thewhole area at the edge of the chip support is subjected to coiningprocessing from the side of the sealed surface (which may be a commonprocess step to the coining processing for forming the slippingpreventing portion). Consequently, the sag occurring at the edge of theexposed surface of the chip support can be reduced or eliminated by thepunching processing from the side of the exposed surface, thereby makingit possible to effectively restrain or prevent the detour of the sealingresin toward the exposed surface of the chip support.

It is preferable that the method further includes a step of forming alead to be electrically connected to the semiconductor chip withinsealing resin and to be sealed into the sealing resin such that at leasta part of its mounting surface which is a surface on the same side ofthe exposed surface of the chip support is exposed from the sealingresin, a step of forming a hang lead for coupling the chip support to aframe for holding the lead, and a down-setting step for molding the hanglead and positioning the exposed surface of the chip support so as toproject in the direction away from the lead on the same side of themounting surface of the lead.

According to this method, the exposed surface of the chip support ispositioned so as to project beyond the mounting surface of the lead.When the lead is resin-sealed in a state where the mounting surface ofthe lead and the exposed surface of the chip support are pressed againsta flat surface of a metal mold, the hang lead is elastically deformed,to apply a pressing force against the metal mold to the chip support.This makes it possible to restrain and prevent the detour of the resintoward the exposed surface of the chip support, realizing asemiconductor device having good heat dissipation efficiency.

It is preferable that the hang lead is molded by press working.Consequently, the lead frame can be fabricated at low cost.

It is preferable that the hang lead is also formed by punchingprocessing from the same side of the exposed surface.

A method of fabricating a lead frame according to a third aspect of thepresent invention is a method of fabricating a lead frame for asemiconductor device having a semiconductor chip resin-sealed therein,the lead frame including a chip support to have the semiconductor chipcarried thereon and having one surface serving as an exposed surfaceexposed from the sealing resin and the other surface serving as a sealedsurface sealed into the sealing resin, and a lead to be electricallyconnected to the semiconductor chip within the sealing resin and sealedinto the sealing resin such that at least a part of its mounting surfacewhich is a surface on the same side of the exposed surface is exposedfrom the sealing resin. The method includes a step of shaping a metalplate to form the lead, a step of shaping the metal plate to form thechip support, a step of forming a hang lead for coupling the chipsupport to a frame for holding the lead, and a down-setting step formolding the hang lead and positioning the exposed surface of the chipsupport so as to project in the direction away from the lead on the sameside of the mounting surface of the lead.

It is preferable that the down-setting step includes a step of moldingor forming the hang lead so as to have an up-set portion offset in thedirection away from the lead on the opposite side of the mountingsurface of the lead and a connecting portion for connecting the up-setportion and the chip support to each other. According to this method,the hang lead has a wavy shape. When the chip support is pressed againstthe flat surface of the metal mold, the hang lead is easily elasticallydeformed, thereby making it possible to restrain relative displacement(relative displacement as viewed from the top) between the chip supportand the lead.

A method of fabricating a semiconductor device according to a secondaspect of the present invention is a method of fabricating asemiconductor device, including: a step of fabricating the lead frame bythe above-mentioned method; a step of carrying the semiconductor chip onthe sealed surface of the chip support; and a step of resin-sealing thelead frame, together with the semiconductor chip, such that the exposedsurface of the chip support is exposed.

It is preferable that the resin sealing step includes a step of sealingthe lead and the chip support with the sealing resin in a state wherethe mounting surface of the lead and the exposed surface of the chipsupport in the lead frame are pressed against a flat surface of a metalmold. According to this method, the semiconductor device in a statewhere the mounting surface of the lead and the exposed surface of thechip support are exposed from the sealing resin is obtained.

A lead frame according to a second aspect of the present invention is alead frame for a semiconductor device having a semiconductor chipresin-sealed therein, including a chip support to have the semiconductorchip carried thereon and having one surface serving as an exposedsurface exposed from sealing resin and the other surface serving as asealed surface to be sealed into the sealing resin, and a slippingpreventing portion sticking out sideward from an edge of the chipsupport at an intermediate position in the thickness direction of thechip support and formed by subjecting the edge of the chip support tocoining processing from the side of the exposed surface or the sealedsurface.

It is preferable that the lead frame further includes a lead to beelectrically connected to the semiconductor chip within the sealingresin and to be sealed into the sealing resin such that at least a partof its mounting surface which is a surface on the same side of theexposed surface is exposed from the sealing resin, and a hang leadformed so as to couple the chip support to a frame for holding the leadand to position the exposed surface of the chip support as projecting inthe direction away from the lead on the same side of the mountingsurface of the lead.

A lead frame according to a third aspect of the present invention is alead frame for a semiconductor device having a semiconductor chipresin-sealed therein, including a chip support to have the semiconductorchip carried thereon and having one surface serving as an exposedsurface exposed from the sealing resin and the other surface serving asa sealed surface to be sealed into the sealing resin, a lead to beelectrically connected to the semiconductor chip within the sealingresin and to be sealed into the sealing resin such that at least a partof its mounting surface which is a surface on the same side of theexposed surface is exposed from the sealing resin, and a hang leadmolded or formed so as to couple the chip support to a frame for holdingthe lead and to position the exposed surface of the chip support asprojecting in the direction away from the lead on the same side of themounting surface of the lead.

It is preferable that the mounting surface of the lead and a surface, onthe same side of the mounting surface, of the frame are positioned so asto be substantially flush with each other.

It is preferable that the hang lead includes an up-set portion offset inthe direction away from the lead on the opposite side of the mountingsurface of the lead, and a connecting portion for connecting the up-setportion and the chip support to each other.

A semiconductor device according to a second aspect of the presentinvention is a semiconductor device comprising: the above-mentioned leadframe; the semiconductor chip carried on the sealed surface of the chipsupport in the lead frame; and the sealing resin for sealing the leadframe and the semiconductor chip such that the mounting surface of thelead and the exposed surface of the chip support in the lead frame areexposed with the surfaces being flush with each other.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the configuration of a lead frameaccording to an embodiment of the present invention;

FIG. 2 is an illustrative sectional view showing the configuration of asemiconductor device having the lead frame incorporated therein;

FIG. 3 (a) is a plan view of a lead 2, FIG. 3 (b) is a longitudinalsectional view (a cross-sectional view taken along a line IIIB-IIIB) ofFIG. 3 (a), and FIG. 3 (c) is a transverse sectional view (across-sectional view taken along a line IIIC-IIIC) of FIG. 3 (a);

FIG. 4 is a conceptual diagram for explaining the configuration of aprecision press apparatus used for fabricating the lead frame;

FIGS. 5 (a), 5 (b), and 5 (c) are illustrative sectional views forrespectively explaining the configurations of press stations in theprecision press apparatus;

FIG. 6 is an illustrative sectional view showing the configuration of asemiconductor device according to another embodiment of the presentinvention;

FIG. 7 is a plan view showing the configuration of a lead frameaccording to still another embodiment of the present invention;

FIGS. 8 (a) and 8 (b) are illustrative sectional views showing theconfiguration of a semiconductor device having a lead frame incorporatedtherein;

FIG. 9 (a) is a partially enlarged plan view of a support in the leadframe, FIG. 9 (b) is a longitudinal sectional view (a cross-sectionalview taken along a line IXB-IXB in FIG. 9 (a)) of a support and a hanglead, and FIG. 9 (c) is a transverse sectional view (a cross-sectionalview taken along a line IXC-IXC in FIG. 9 (a)) at an edge of thesupport;

FIG. 10 is a conceptual diagram for explaining the configuration of aprecision press apparatus used for fabricating the lead frame;

FIGS. 11 (a) to 11 (d) are illustrative sectional views for respectivelyexplaining the configurations of press stations in the precision pressapparatus;

FIG. 12 is a cross-sectional view showing the cross-sectional shape of asupport after punching processing;

FIGS. 13 (a) and 13 (b) are illustrative sectional views for explaininga resin sealing step;

FIG. 14 is a cross-sectional view of an edge of a support in a leadframe according to still another embodiment of the present invention;

FIG. 15 is a plan view of a lead frame according to a further embodimentof the present invention; and

FIGS. 16 (a) and 16 (b) are plan views showing a lead frame according toa still further embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a plan view showing the configuration of a lead frameaccording to an embodiment of the present invention. FIG. 1 illustratesa unit portion corresponding to one semiconductor device. But inpractice, unit portions corresponding to a plurality of semiconductordevices are connected to one another in a left-to-right direction inFIG. 1, thereby constituting a band-shaped chain member as a whole.

The lead frame 10 is fabricated by subjecting a metal plate(particularly a copper plate, for example, having a plate thickness ofapproximately 200 μm) 100 to precision press processing. A unit portioncorresponding to one semiconductor device has a rectangular shape (anapproximately square shape in an example of FIG. 1), and has a support(an island) 1 for supporting a semiconductor chip at its center and hasa plurality of leads 2 arranged at approximately equal spacing so as toform an imaginary rectangular shape around its periphery.

The support 1 has a rectangular shape corresponding to the imaginaryrectangular shape formed by the plurality of leads 2, and is coupled toa frame 5 connecting with the metal plate 100 through hang leads 4 atfour corners of the rectangular shape in the present embodiment. Each ofthe leads 2 has a longitudinal shape arranged with its front enddirected toward the support 1, and has its base end coupled to the frame5. The plurality of leads 2 arranged along each of the sides of theimaginary rectangular shape are parallel to one another, and thelongitudinal direction thereof is along a direction nearly perpendicularto the side. Reference numerals 101, 102, and 103 denote positioningholes for positioning the lead frame 10 in a processing step in each ofpress stations in a precision press apparatus, a mounting step formounting the semiconductor chip, a sealing step for sealing with sealingresin, and so on.

FIG. 2 is an illustrative sectional view showing the configuration of asemiconductor device having the above-mentioned lead frame 10incorporated therein. The semiconductor device comprises the lead frame10, a semiconductor chip 6 mounted on the support 1 in the lead frame10, a bonding wire 7 for electrically connecting the semiconductor chip6 and an upper surface 2 a (a sealed surface) of the lead 2 to eachother, and sealing resin 8 for sealing them. A lower surface (a mountingsurface) 2 b of the lead 2 is exposed from a lower surface of thesealing resin 8, and functions as an outer lead soldered and joined to awiring pattern on a circuit board. Further, a portion, sealed into thesealing resin, of the lead 2 functions as an inner lead, and a portionnear its front end is an inner connecting portion to which the bondingwire 7 is joined. A surface-mounting type semiconductor package (QFN) isthus configured.

In assembling the semiconductor device, the semiconductor chip 6 isdie-bonded to an upper surface of the support 1, and a terminal of thesemiconductor chip 6 and the upper surface 2 a of the lead 2 areconnected to each other by the bonding wire 7. Thereafter, an areawithin a sealing line 50 indicated by a two-dot and dash line in FIG. 1is resin-sealed with the lower surface 2 b of the lead 2 pressed againsta metal mold. Consequently, the semiconductor chip 6, the bonding wire7, and the lead 2 are resin-sealed to form a package. Thereafter, thelead 2 and the hang lead 4 are cut along a side surface of the package,and are cut away from the frame 5. Respective pieces of thesemiconductor device are thus obtained.

FIG. 3 (a) is a plan view of the lead 2, FIG. 3 (b) is a longitudinalsectional view (a cross-sectional view taken along a line IIIB-IIIB) ofFIG. 3 (a), and FIG. 3 (c) is a transverse sectional view (across-sectional view taken along a line IIIC-IIIC) of FIG. 3 (a).Slipping preventing portions 21, 22, 23, and 24 (whose illustration isomitted in FIG. 1) are respectively formed at four positions, two ofwhich are spaced apart from each other in the longitudinal direction ateach of both side edges of the upper surface 2 a of the lead 2. In thepresent embodiment, the slipping preventing portions 21, 22, 23, and 24are provided in an area on the side of the support 1 with respect to acutting line 51 along which the lead 2 is cut after resin sealing sothat the sealing line 50 passes through an intermediate portion in thelongitudinal direction of the pair of slipping preventing portions 23and 24 on the side of the base end of the lead 2. Consequently, the pairof slipping preventing portions 21 and 22 on the side of the front endof the lead 2 enters the sealing resin 8, and the sealing resin 8 alsoenters between the pair of slipping preventing portions 21 and 22 andthe pair of slipping preventing portions 23 and 24. Thus, the slippingpreventing portions 21, 22, 23, and 24 can prevent the lead 2 fromslipping off in the longitudinal direction.

The slipping preventing portions 21, 22, 23, and 24 are formed bysubjecting their side edges to coining processing from the side of theupper surface 2 a of the lead 2. More specifically, in an area above arectangular outer lead to be exposed from the lower surface of thesealing resin 8 after resin sealing on the lower surface 2 b of the lead2, both the side edges of the upper surface 2 a of the lead 2 aresubjected to coining processing. Consequently, the slipping preventingportions 21, 22, 23, and 24 respectively have upper surfaces lower thanthe upper surface 2 a and have lower surfaces (slipping preventingsurfaces, which are inclined surfaces directed upward as they separatefrom a side surface of the lead 2 in an example shown in FIG. 3) atpositions sticking out sideward from the side surface of the lead 2 andhigher than the lower surface 2 b of the lead 2. Consequently, thesealing resin 8 detours below parts, which stick out, of the slippingpreventing portions 21 to 24, thereby making it possible to prevent thelead 2 from slipping off the sealing resin 8 downward. For example, thewidth of the coining processing of both the side edges of the uppersurface 2 a for forming the slipping preventing portions 21 to 24 may beapproximately 50 μm (approximately one-fourth to one-third of the widthW of the lead 2 (e.g., approximately 180 to 200 μm)), and the heightthereof may be approximately 50 μm (approximately one-fourth to one-halfof the plate thickness H of the lead 2 (e.g., approximately 200 μm)).

On the upper surface 2 a of the lead 2, an area from the slippingpreventing portions 21 and 22 to the front end (the support 1) functionsas a wire connecting portion (an inner connecting portion) to which thebonding wire 7 is joined. A plating layer 29 (e.g., a silver platinglayer having a thickness of not more than 5 μm, whose illustration isomitted in FIGS. 1 and 3 (a)) for good joining to the bonding wire 7 isformed in the wire connecting portion. The lower surface 2 b of the lead2, together with the semiconductor chip 6, is resin-sealed and is thenexposed from the lower surface of the sealing resin 8, to function as anouter connecting portion (an outer lead) for surface-mounting on thecircuit board.

An area at the front end of the lead 2 is subjected to coiningprocessing from the side of the lower surface 2 b of the lead 2, and afront end slipping preventing portion 25 offset upward from the lowersurface 2 b of the lead 2 (e.g., by approximately one-third to one-halfof the plate thickness H of the lead 2) is formed. The front endslipping preventing portion 25 sticks out, on the upper surface 2 a ofthe lead 2, toward its front end. In a state where the lead 2, togetherwith the semiconductor chip 6, is resin-sealed, the sealing resin 8detours below the front end slipping preventing portion 25, therebypreventing the lead 2 from slipping off.

FIG. 4 is a conceptual diagram for explaining the configuration of theprecision press apparatus used for fabricating the lead frame 10. Thelead frame 10 is conveyed in a forward direction R successively througha plurality of (four in an example shown in FIG. 4) press stations S1 toS4. The press station S1 is a punching processing portion for subjectingthe band-shaped metal plate 100 which is a material to punchingprocessing from the side of its lower surface. The press station S2 is afront end lower surface coining processing portion for subjecting thefront end of the lead 2 to coining processing from the side of the lowersurface 2 b of the lead 2. The press station S3 is a cutting processingportion for cutting the front end of the lead 2 at a cutting positionhaving a predetermined length from the side of the base end of the lead2. The press station S4 is a upper surface coining processing portionfor subjecting both side edges of the upper surface 2 a of the lead 2 tocoining processing to form the slipping preventing portions 21 to 24.

FIG. 5 (a) is an illustrative sectional view showing the configurationof the press station S1 (punching processing portion), showing a crosssection taken along a plane crossing the longitudinal direction of thelead 2. In the press station S1, the band-shaped metal plate 100 issubjected to punching processing from the side of the lower surface 100b. More specifically, the metal plate 100 is inserted between a die 61and a suppressing member 71 respectively having openings 61 a and 71 acorresponding to a pattern of the support 1, the lead 2, or the like. Inthis state, a punch 81 having a shape conforming to the openings 61 aand 71 a is moved up and down such that it passes through the openings71 a and 61 a to form a hole in the metal plate 100 in a direction fromits lower surface 100 b to its upper surface 100 a, and then it retreatsfrom the openings 61 a and 71 a. Consequently, the support 1 and thelead 2 are formed by punching processing from the side of the lowersurface 2 b of the lead 2.

FIG. 5 (b) is an illustrative sectional view showing the configurationof the press station S2 (front end lower surface coining processingportion), showing a state as viewed from the side surface of the lead 2.In the press station S2, the front end slipping preventing portion 25 isformed by coining processing from the side of the lower surface 2 b atthe front end of the lead 2 obtained by punching processing. Morespecifically, a die 62 having a flat lower surface is arranged above thelead 2, and a suppressing member 72 is arranged below the metal plate100. A punch 82 is moved up and down with a predetermined stroke (astroke corresponding to coining processing which is approximatelyone-third to one-half the plate thickness H of the lead 2) through anopening 72A formed in the suppressing member 72.

The punch 82 is overlapped with the front end of the lead 2. Therefore,the front end of the lead 2 is coined, and is offset upward from thelower surface 2 b of the lead 2. Consequently, the above-mentioned frontend slipping preventing portion 25 is formed.

The stroke of the punch 82 is so determined as to be lowered after anupper end of the punch 82 is moved to an intermediate position of theplate thickness of the metal plate 100.

FIG. 5 (c) is an illustrative sectional view showing the configurationof the press station S4 (upper surface coining processing portion),showing a cross section taken along a plane crossing the longitudinaldirection of the lead 2. After the front end slipping preventing portion21 is cut to a predetermined length in the press station S3, both theside edges of the upper surface 2 a of the lead 2 are subjected tocoining processing in the press station S4. In the press station S4, adie 63 having a flat upper surface is arranged below the leads 2, andsuppressing members 73 respectively having openings 73 a wider thanspacing between the adjacent leads 2 at corresponding positions betweenthe adjacent leads 2 are arranged above the leads 2. A punch 83 whichmoves up and down through an opening 73 a is arranged above thesuppressing member 73. The punch 83 has a pressing surface 83A widerthan spacing between the adjacent leads 2 at its lower end.

The stroke of the punch 83 is so determined that the position of itslower dead point is within a range of the plate thickness of the mainbody 20 of the lead 2. By moving the punch 83 up and down, therefore,both the side edges of the lead 2 are pressed from the side of the uppersurface 2 a over a width of approximately 50 μm (a range which isone-fourth to one-third the width W (e.g., approximately 180 to 200 μm)of the lower surface 2 b of the lead 2) and a height of approximately 50μm (a range which is one-fourth to one-half the plate thickness H of thelead 2 (e.g., approximately 200 μm)). Consequently, the slippingpreventing portions 21 to 24 are formed so as to project on both theside surfaces of the lead 2. Correspondingly, the lower surface 2 b ofthe lead 2 is pressed against the die 63, so that a sag occurring at thetime of punching processing is flattened.

When the lead frame 10 is thus formed through the press stations S1 toS4, the wire connecting portion is subjected to plating processing(e.g., silver plating processing).

In the present embodiment, the first form of the lead 2 formed bypunching processing has a simple form which is approximately rectangularin cross section and is uniform in the longitudinal direction, and awide part or a constricted part need not be formed therein, as in theabove-mentioned prior art. Consequently, the forms of the punch 81, thedie 61, and so on for punching processing are not complicated, and theirfabrication costs are not too high. Therefore, the fabrication costs ofthe lead frame 10 and the semiconductor device having the lead frame 10incorporated therein can be reduced.

Moreover, the slipping preventing portions 21 to 24 are formed bycoining processing not from the side of the lower surface 2 b of thelead 2 but from above both the side edges of the upper surface 2 a ofthe lead 2. Therefore, the side edges of the lower surface 2 b of thelead 2 serving as an outer lead can keep its initial linear shape,thereby making it possible to ensure good mounting properties on thewiring substrate.

No burr occurs in the above-mentioned coining processing from above boththe side edges of the upper surface 2 a of the lead 2 having theabove-mentioned simple form, so that no special measures as in theabove-mentioned prior art are required.

Although in the above-mentioned embodiment, the slipping preventingportions 21 to 24 are respectively formed at four positions, two ofwhich are spaced apart from each other along the longitudinal directionat each of both side edges of the upper surface 2 a of the lead 2, onesimilar slipping preventing portion or three or more similar slippingpreventing portions may be formed at each of the side edges of the uppersurface 2 a of the lead 2. Slipping preventing portions over almost theentire length of the lead 2 may be formed by coining processing at boththe side edges of the upper surface 2 a. Similar slipping preventingportion or portions may be formed only at one of the side edges of theupper surface 2 a of the lead 2.

Although in the above-mentioned embodiment, description has been made ofan example in which the lead 2 and the semiconductor chip 6 areelectrically connected to each other through the bonding wire 7, thelead 2 and the semiconductor chip 6 may be connected to each otherwirelessly by providing a bump B at the terminal of the semiconductorchip 6 and joining the bump B to the upper surface 2 a of the lead 2, asshown in FIG. 6. Before the joining, the bump B may be provided in atleast one of the semiconductor chip 6 and the lead 2. That is, the bumpB may be provided in the lead 2. Alternatively, bumps may berespectively provided in both the semiconductor chip 6 and the lead 2.

Although in the above-mentioned embodiment, in the steps of processingthe metal plate 100 to fabricate the lead frame 10, processing by thepress station S1 to S4 is performed in a state where the upper surfaceof the lead frame 10 is directed upward and the lower surface thereof isdirected downward, the processing in each of the steps may be performedin a state where the upper surface of the lead frame 10 is directeddownward and the lower surface thereof is directed upward. In this case,the vertical relationship among the punch, the suppressing member, andthe die in the press stations S1 to S4 is preferably reversed.

Although in the above-mentioned embodiment, a series of processing stepsfor fabricating the lead frame 10 is continuously performed by oneprecision press apparatus, some of the steps may be performed by anotherapparatus.

FIG. 7 is a plan view showing the configuration of a lead frameaccording to another embodiment of the present invention. FIG. 7illustrates a unit portion corresponding to one semiconductor device.But in practice, unit portions corresponding to a plurality ofsemiconductor devices are connected to one another in a left-to-rightdirection in FIG. 7, thereby constituting a band-shaped chain member asa whole.

The lead frame 150 is fabricated by subjecting a metal plate(particularly a copper plate, for example, having a plate thickness ofapproximately 200 μm) 200 to precision press processing. A unit portioncorresponding to one semiconductor device has a rectangular shape (anapproximately square shape in an example of FIG. 7), and has a support(an island) 301 for supporting a semiconductor chip at its center andhas a plurality of leads 302 arranged at approximately equal spacing soas to form an imaginary rectangular shape around its periphery.

A support 301 has a rectangular shape as viewed from the top and iscoupled to a frame 305 connecting with the metal plate 200 through hangleads 4 at four corners of the imaginary rectangular shape formed by theplurality of leads 302 in the present embodiment. Each of the leads 302has a longitudinal shape arranged with its front end directed toward thesupport 301, and has its base end coupled to the frame 305. Theplurality of leads 302 arranged along each of the sides of therectangular shape are parallel to one another, and the longitudinaldirection thereof is along a direction nearly perpendicular to the side.Reference numerals 201, 202, and 203 denote positioning holes forpositioning the lead frame 150 in a processing step in each of pressstations in a precision press apparatus, a mounting step for mountingthe semiconductor chip, a sealing step for sealing with the sealingresin, and so on.

FIG. 8 (a) is an illustrative sectional view showing the configurationof a semiconductor device having the above-mentioned lead frame 150incorporated therein. The semiconductor device comprises the lead frame150, a semiconductor chip 306 mounted on the support 301 in the leadframe 150, a bonding wire 307 for electrically connecting thesemiconductor chip 306 and an upper surface 302 a of the lead 302 toeach other, and sealing resin 308 for sealing them.

A lower surface 302 b serving as a mounting surface of the lead 302 isexposed from a lower surface of the sealing resin 308, and functions asan outer lead soldered and joined to a wiring pattern on a circuitboard. Further, a portion, sealed into the sealing resin 308, of thelead 302 functions as an inner lead, and a portion near its front end isan inner connecting portion to which the bonding wire 307 is joined. Onthe other hand, the support 301 has its lower surface serving as anexposed surface exposed from the lower surface of the sealing resin 308,and heat generated by the semiconductor chip 306 is dispersed throughthe lower surface of the support 301. A surface-mounting typesemiconductor package (HQFN) having a heat dispersion structure is thusconfigured.

In assembling the semiconductor device, the semiconductor chip 306 isdie-bonded to an upper surface (sealed surface) of the support 301, anda terminal of the semiconductor chip 306 and the upper surface 302 a ofthe lead 302 are connected to each other by the bonding wire 307.Thereafter, a sealing area 350 indicated by a two-dot and dash line inFIG. 7 is resin-sealed. Consequently, the semiconductor chip 306, thebonding wire 307, and the lead 302 are resin-sealed to form a package.Thereafter, the lead 302 and the hang lead 304 are cut along a sidesurface of the package, and are cut away from the frame 305. Respectivepieces of the semiconductor device are thus obtained.

The upper surface 302 a of the lead 302 functions as a wire connectingportion (an inner connecting portion) to which the bonding wire 7 isjoined. A plating layer 329 (e.g., a silver plating layer having athickness of not more than approximately 5 μm) for good joining to thebonding wire 307 is formed in the wire connecting portion. On the otherhand, the lower surface 302 b of the lead 302, together with thesemiconductor chip 306, is resin-sealed and is then exposed from thelower surface of the sealing resin 308, to function as an outerconnecting portion (an outer lead) for surface-mounting on the circuitboard.

An area at the front end, on the side of the support 301, of the lead302 is subjected to coining processing from the side of the lowersurface 302 b of the lead 302, and a front end slipping preventingportion 321 offset upward from the lower surface 302 b of the lead 302by approximately one-third to one-half of the plate thickness of thelead 302 is formed. The front end slipping preventing portion 321 sticksout, on the upper surface 302 a of the lead 302, toward its front end.In a state where the lead 302, together with the semiconductor chip 306,is resin-sealed, the sealing resin 308 detours below the front endslipping preventing portion 321, thereby preventing the lead 302 fromslipping off.

FIG. 8 (b) is a diagram showing a cross-sectional shape along a diagonalline in a rectangular shape formed by a plurality of leads 302. In astate where the lead 302 is sealed with the sealing resin 308, a lowersurface 301 b of the support 301, the lower surface 302 b of the lead302, and a lower surface 304 b at an outer end (a base end) of the hanglead 304, together with the lower surface of the sealing resin 308, arepositioned so as to be flush with one another. The hang lead 304comprises an elastic deformation portion 345 having an up-set portion341 set upward with respect to the support 301 and a connecting portion342 for connecting the up-set portion 341 to the support 301. Before thelead 302 is sealed with the sealing resin 308, the support 301 is setdownward with respect to the lead 302. At the time of resin sealing, theelastic deformation portion 345 is elastically deformed so that theelastic deformation portion 345 is arranged so as to be flush with thelead 302.

FIG. 9 (a) is a partially enlarged plan view of the support 301, FIG. 9(b) is a longitudinal sectional view (a cross-sectional view taken alonga line IXB-IXB in FIG. 9 (a)) of the support 301 and the hang lead 304,and FIG. 9 (c) is a transverse sectional view (a cross-sectional viewtaken along a line IXC-IXC in FIG. 9 (a)) at an edge of the support 301.In almost the whole area of each of the sides of the rectangular support301, a slipping preventing projection 331 by coining processing from theside of an upper surface of the support 301 is formed. The slippingpreventing projection 331 has an upper surface 331 a lower than theupper surface 301 a of the other part of the support 301 by the heightof the coining processing (e.g., approximately one-fourth to one-half ofthe plate thickness of the support 301) and a lower surface 331 b higherthan the lower surface 301 b of the support 301, and projects sidewardfrom an intermediate position of the plate thickness on the side surfaceof the support 301. When the lead 302 is sealed with the sealing resin308, therefore, the sealing resin 308 detours below the slippingpreventing projection 331, thereby making it possible to prevent thesupport 301 from slipping off the sealing resin 308 downward. The widthof the coining processing is approximately 50 to 70 μm, for example.

On the other hand, the hang lead 304 connects the support 301 and theframe 305 to each other such that the lower surface 301 b of the support301 is set downward to a position lower than a lower surface 305 b ofthe frame 305 (e.g., the difference in height is less than the platethickness, which is approximately 50 μm to 150 μm), as shown in FIG. 9(b). The lower surface 305 b of the frame 305 is flush with the lowersurface 302 b of the lead 302. Therefore, the support 301 is eventuallyset downward such that the lower surface 301 b is lower than the lowersurface 302 b of the lead 302 (the whole of the support 301 is lowerthan the lower surface 302 b of the lead 302 in the present embodiment).

More specifically, the hang lead 304 has the up-set portion 341 setupward to a position higher than an upper surface 305 a of the frame 305on the side of the frame 305. The up-set portion 341 and the support 301are connected to each other by the connecting portion 342. Theconnecting portion 342 is formed in an inclined posture which fallstoward the support 301, to support the support 301 at a position lowerthan the lower surface 305 b of the frame 305. That is, the hang lead304 is roughly molded in an S shape, and the elastic deformation portion345 including the up-set portion 341 and the connecting portion 342 iselastically deformed to allow the up-and-down motion of the support 301while holding the relative positional relationship as viewed from thetop among the support 301, the frame 305, and the lead 302 when anexternal force in the vertical direction is applied to the support 301.

FIG. 10 is a conceptual diagram for explaining the configuration of theprecision press apparatus used for fabricating the lead frame 150. Thelead frame 150 is conveyed in a forward direction R10 successivelythrough a plurality of (five in an example shown in FIG. 10) pressstations S11 to S15. The press station S11 is a punching processingportion for subjecting the band-shaped metal plate 200 which is amaterial to punching processing from the side of its lower surface. Thepress station S12 is a front end lower surface coining processingportion for subjecting the front end of the lead 302 to coiningprocessing from the side of the lower surface 302 b. The press stationS13 is a cutting processing portion for cutting the front end of thelead 302 at a cutting position having a predetermined length from theside of the base end of the lead 302. The press station S14 is a coiningprocessing portion for subjecting the whole area at the edge of thesupport 301 to coining processing from the side of the upper surface 301a. The press station S15 is a hang lead molding processing portion formolding the hang lead 304 in the above-mentioned S shape.

FIG. 11 (a) is an illustrative sectional view showing the configurationof the press station S11 (punching processing portion), showing a crosssection of a portion corresponding to the support 301. In the pressstation S11, the band-shaped metal plate 200 is subjected to punchingprocessing from the side of the lower surface 200 b. More specifically,the metal plate 200 is inserted between a die 361 and a suppressingmember 371 respectively having openings 361 a and 371 a corresponding toa pattern of the support 301, the lead 302, or the like. In this state,a punch 381 having a shape conforming to the openings 361 a and 371 a ismoved up and down such that it passes through the openings 371 a and 361a such to form a hole in the metal plate 200 in the direction from itslower surface 200 b to its upper surface 200 a, and then it retreatsfrom the openings 361 a and 371 a. Consequently, the support 301 and thelead 302 are formed by punching processing from the side of the lowersurface 302 b of the lead 302. Consequently, a burr occurring by thepunching processing does not project downward but is sealed into thesealing resin 308 after resin sealing. Therefore, a posterior processingstep for eliminating the burr is not required. By the punchingprocessing from the side of the lower surface 301 b, however, an edge onthe side of the lower surface 301 b is brought into a curved surface asshown in FIG. 12, so that a so-called sag occurs at the edge of thesupport 301.

FIG. 11 (b) is an illustrative sectional view showing the configurationof the press station S12 (front end lower surface coining processingportion), showing a state as viewed from the side surface of the lead302. In the press station S12, the front end slipping preventing portion321 is formed by coining processing from the side of the lower surface302 b at the front end of the lead 302 obtained by punching processing.More specifically, a die 362 having a flat lower surface is arrangedabove the lead 302, and a suppressing member 372 is arranged below themetal plate 200. A punch 382 is moved up and down with a predeterminedstroke through an opening 372A formed in the suppressing member 372. Thestroke of the punch 382 is so determined as to be lowered after an upperend of the punch 382 is moved to an intermediate position of the platethickness of the metal plate 200.

The punch 382 is overlapped with the front end of the lead 302.Therefore, the front end of the lead 302 is coined and is offset upwardfrom the lower surface 302 b of the lead 302. Consequently, theabove-mentioned front end slipping preventing portion 321 is formed.

FIG. 11 (c) is an illustrative sectional view showing the configurationof the press station S14 (coining processing portion), showing aconfiguration taken along the same cross section as that shown in FIG. 9(c). After the front end slipping preventing portion 321 is cut to apredetermined length in the press station S13, the entire edge of thesupport 301 is subjected to coining processing from the side of theupper surface 301 a. That is, in the press station S14, a die 364 havinga flat upper surface is arranged below the support 301, and asuppressing member 374 for pressing portions, corresponding to the lead302, the frame 305, and so on, other than the support 301 is arrangedabove the metal plate 200, as shown in FIG. 11 (c). The suppressingmember 374 is formed with an opening 374 a for exposing the entire edgeof the support 301, and is provided with a punch 384 so as to be movableup and down through the opening 374 a. The punch 384 has a pressingsurface 384 a which can press the entire edge of the support 301 on itslower surface.

The up-and-down stroke of the punch 384 is so set that the position of alower dead point of the pressing surface 384 a is below (e.g., onlyone-fourth to one-half of the plate thickness of the lead 302 below) theupper surface 302 a of the lead 302 before the coining processing.

The cross-sectional shape of the support 301 after the coiningprocessing from the side of the upper surface 301 a is as shown in FIG.9 (c). That is, the above-mentioned slipping preventing projection 331is formed by the coining processing of the edge from the side of theupper surface 331 a. Correspondingly, the sag occurring at the edge ofthe lower surface is eliminated by the coining processing from the sideof the upper surface 331 a. Accordingly, the support 301 is anapproximately flat plane up to its edge, and the edge is a raisedsurface which is raised at an angle of approximately 90 degrees. Whenthe lead 302 is sealed with the sealing resin 308, therefore, thesealing resin 308 can be prevented from effectively detouring toward theedge of the lower surface 301 b of the support 301.

FIG. 11 (d) is an illustrative sectional view showing the configurationof the press station S15 (hang lead molding processing portion), showinga cross section along the longitudinal direction of the hang lead 304.In the press station S15, a die 365 having an irregular pattern,corresponding to the shapes of the lower surfaces of the hang lead 304and the support 301 after molding, carved on its upper surface isarranged below the hang lead 304 and the support 301, and a punch 385having an irregular pattern, corresponding to the shapes of the uppersurfaces of the hang lead 304 and the support 301 after molding, carvedon its lower surface is arranged above the hang lead 304 and the support301. A suppressing member 375 having an opening 375 a corresponding toareas of the hang lead 304 and the support 301 is arranged above themetal plate 200, and the punch 385 can be moved up and down with apredetermined stroke through the opening 375 a.

The metal plate 200 is subjected to press molding processing by movingthe punch 385 up and down to apply pressure with the metal plate 200interposed between respective carving surfaces of the punch 385 and thedie 365. Consequently, the hang lead 304 is molded in theabove-mentioned shape having the up-set portion 341 and the connectingportion 342, and the support 301 is set downward with respect to thelower surface of the frame 305.

When the lead frame 150 is thus formed through the press stations S11 toS15, the wire connecting portion is subjected to plating processing(e.g., silver plating processing). The plating processing may beperformed before the hang lead molding processing step by the pressstation S15.

FIGS. 13 (a) to 13 (e) are illustrative sectional views for explainingthe resin sealing step, where FIG. 13 (a) illustrates a cross sectioncorresponding to that shown in FIG. 8 (a), and FIG. 13 (b) illustrates across section corresponding to that shown in FIG. 8 (b).

An assembly obtained by die-bonding the semiconductor chip 306 on theupper surface of the support 301 in the lead frame 150 fabricated in theabove-mentioned manner and electrically connecting the terminal (pad) ofthe semiconductor chip 306 and the lead 302 to each other using thebonding wire 307 is placed between a lower metal mold 110 having a flatupper surface and an upper metal mold 120 having a recess forming acavity 115 into which the sealing resin 308 flows on its lower surface.

The upper metal mold 120 has paths 116 and 117 for respectively pullingthe base ends of the lead 302 and the hang lead 304 out of the cavity115 formed on its lower surface. When the upper metal mold 120 and thelower metal mold 110 are abutted against each other in close proximity,each of the base ends of the lead 302 and the hang lead 304 isinterposed between the upper metal mold 120 and the lower metal mold 110within the paths 116 and 117.

On the other hand, the support 301 is set downward with respect to thelead 302. Therefore, the support 301 is pushed upward in the step ofinterposing the lead 302 and the hang lead 304 by the upper metal mold120 and the lower metal mold 110, so that the elastic deformationportion 345 in the hang lead 304 is elastically deformed. Finally, thelower surface 301 b of the support 301 and the lower surface 302 b ofthe lead 302 are arranged so as to be flush with each other. At thistime, the support 301 is pressed against the flat upper surface of thelower metal mold 110 due to a restoring force of the hang lead 304. Ifthe sealing resin 308 is injected into the cavity 115 in this state, theabove-mentioned assembly can be satisfactorily sealed without causingthe sealing resin 308 to detour toward the lower surface of the support301. Consequently, the semiconductor device finally obtained cansatisfactorily disperse heat generated by the semiconductor chip 306from the lower surface of the support 301.

FIG. 14 is a diagram for explaining the configuration of a still anotherembodiment of the present invention, illustratively showing the crosssection of a support for supporting a semiconductor chip. In theabove-mentioned embodiment, the upper surface 301 a at the edge of thesupport 301 is subjected to coining processing to form the slippingpreventing projection 331. On the other hand, in the present embodiment,a lower surface 301 b at an edge of the support 301 is subjected tocoining processing to form a slipping preventing projection 332 havingthe same function. The slipping preventing projection 332 has a lowersurface 332 b offset upward from the lower surface 301 b of the support301. Therefore, sealing resin 308 detours below the lower surface 332 b,thereby making it possible to achieve slipping prevention of the support301.

The slipping preventing projection 332 can be formed by a configurationin which the suppressing member 374, the punch 384, and the die 364 arereversed in the vertical direction in the configuration shown in FIG. 11(c).

Although in the above-mentioned embodiment, the whole area at the edgeof the support 301 is subjected to coining processing from the side ofan upper surface 301 a or the lower surface 301 b of the support 301, agood slipping preventing projection 333 can be formed if an area whichis a part of an edge of a support 301 (a plurality of positions spacedapart from one another in an example shown in FIG. 15) is subjected tocoining processing from the side of its upper surface or lower surface,as shown in FIG. 15, for example.

Although in the above-mentioned embodiment, description has been made ofthe example in which the support 301 is formed in a rectangular shape,the support 301 may be formed in an approximately X shape, as shown inFIGS. 16 (a) and 16 (b). In an example shown in FIG. 16 (a), almost thewhole area at an edge of the support 301 in an X shape is subjected tocoining processing from the side of its upper surface or lower surface,thereby forming a slipping preventing projection 334. In an exampleshown in FIG. 16 (b), a slipping preventing projection 335 is formed bysubjecting a part of the edge of the support 301 (specifically, at aplurality of positions spaced apart from one another at each of edges ofthe support 301) to coining processing from the side of the uppersurface or the lower surface.

Although in the above-mentioned embodiment, description has been made ofthe example in which the lead 302 and the semiconductor chip 306 areelectrically connected to each other through the bonding wire 307, abump may be provided at a terminal of the semiconductor chip 306, andmay be joined to the upper surface 302 a of the lead 302.

Although in the above-mentioned embodiment, in the step of processingthe metal plate 200 to fabricate the lead frame 150, processing by eachof the press station S11 to S15 is performed in a state where the uppersurface of the lead frame 150 is directed upward and the lower surfacethereof is directed downward, the processing in each of the steps may beperformed in a state where the upper surface of the lead frame 150 isdirected downward and the lower surface thereof is directed upward. Inthis case, the vertical relationship among the punch, the suppressingmember, and the die in the press stations S11 to S15 is preferablyreversed.

Although in the above-mentioned embodiment, a series of processing stepsfor fabricating the lead frame 150 is continuously performed by oneprecision press apparatus, some of the steps may be performed by anotherapparatus.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

The present application corresponds to Japanese patent application Nos.2003-389770 and 2003-389771 filed with the Japanese Patent Office onNov. 19, 2003, the disclosure of which is hereinto incorporated byreference.

1. A method of fabricating a lead frame for a semiconductor devicehaving a semiconductor chip resin-sealed therein, the lead frameincluding a lead to be electrically connected to the semiconductor chipwithin sealing resin and to be sealed into the sealing resin such thatat least a part of a mounting surface thereof is exposed from thesealing resin, the method comprising: a lead forming step for formingthe lead; a side edge coining step for subjecting a side edge of asealed surface, which is a surface on an opposite side of the mountingsurface, of the lead to coining processing from a side of the sealedsurface, to form a slipping preventing portion projecting sideward fromthe lead and having a slipping preventing surface between the mountingsurface and the sealed surface of the lead; a step of electricallyconnecting the sealed surface of the lead and the semiconductor chip toeach other; a step of resin-sealing the lead frame, together with thesemiconductor chip, such that at least a part of the mounting surface ofthe lead is exposed; and a step of cutting away an unnecessary part ofthe lead frame.
 2. The method according to claim 1, wherein the leadforming step includes a step of forming the lead in a longitudinalshape, and the side edge coining step includes a step of forming theslipping preventing portions at a plurality of positions spaced apartfrom one another in the longitudinal direction of the lead.
 3. Themethod according to claim 1, wherein the lead forming step includes astep of forming the lead in a longitudinal shape, and the side edgecoining step includes a step of forming the slipping preventing portionsat both side edges of the sealed surface of the lead.
 4. The methodaccording to claim 1, wherein the lead forming step includes a punchingprocessing step for a metal plate which is a material for the leadframe.
 5. The method according to claim 1, wherein the step ofresin-sealing the lead frame includes a step of sealing thesemiconductor chip and the lead frame with the sealing resin such thatan end surface of the sealing resin crosses the slipping preventingportion.
 6. A method of fabricating a lead frame for a semiconductordevice having a semiconductor chip resin-sealed therein, the lead frameincluding a chip support to have the semiconductor chip carried thereonand having one surface serving as an exposed surface exposed from thesealing resin and the other surface serving as a sealed surface sealedinto the sealing resin, the method comprising: a step of shaping a metalplate to form the chip support, a step of subjecting an edge of the chipsupport to coining processing from a side of the exposed surface or thesealed surface, and forming a slipping preventing portion sticking outsideward from an edge of the chip support at a position between theexposed surface and the sealed surface of the chip supports a step offorming a lead to be electrically connected to the semiconductor chipwithin the sealing resin and to be sealed into the sealing resin suchthat at least a part of a mounting surface thereof which is a surface onthe same side of the exposed surface of the chic, support is exposedfrom the sealing resin, a step of forming a hang lead for coupling thechip support to a frame holding the lead, and a down-setting step formolding the hang lead and positioning the exposed surface of the chipsupport so as to project in a direction away from the lead on the sameside of the mounting surface of the lead.
 7. The method according toclaim 6, wherein the step of shaping a metal plate to form the chipsupport includes a punching step for punching a hole in the metal platein a shape of the chip support from the exposed surface toward thesealed surface of the chip support.
 8. The method according to claim 6,wherein the down-setting step includes a step of molding the hang leadso as to have an up-set portion offset in a direction away from the leadon the opposite side of the mounting surface of the lead and aconnecting portion for connecting the up-set portion and the chipsupport to each other.
 9. A method of fabricating a lead frame for asemiconductor device having a semiconductor chip resin-sealed therein,the lead frame including a chip support to have the semiconductor chipcarried thereon and having one surface serving as an exposed surfaceexposed from the sealing resin and the other surface serving as a sealedsurface sealed into the sealing resin, and a lead to be electricallyconnected to the semiconductor chip within the sealing resin and to besealed into the sealing resin such that at least a part of a mountingsurface thereof which is a surface on the same side of the exposedsurface is exposed from the sealing resin, the method comprising: a stepof shaping a metal plate to form the lead; a step of shaping the metalplate to form the chip support; a step of forming a hang lead forcoupling the chip support to a frame holding the lead; and adown-setting step for molding the hang lead and positioning the exposedsurface of the chip support so as to project in a direction away fromthe lead on the same side of the mounting surface of the lead, whereinthe down-setting step includes a step of molding the hang lead so as tohave an up-set portion offset in a direction away from the lead on theopposite side of the mounting surface of the lead and a connectingportion for connecting the up-set portion and the chip support to eachother.
 10. A method of fabricating a semiconductor device, comprising; astep of fabricating the lead frame by the method according to claim 6; astep of mounting the semiconductor chip on the sealed surface of thechip support; and a step of resin-sealing the lead frame, together withthe semiconductor chip, such that the exposed surface of the chipsupport is exposed.
 11. The method according to claim 10, wherein thestep of resin-sealing the lead frame includes a step of sealing the leadand the chip support with the sealing resin in a state where themounting surface of the lead and the exposed surface of the chip supportin the lead frame are pressed against a flat surface of a metal mold.